Article (website)  (2008)  
 
Rosa acicularis In Crane, M. F. 1990. Rosa acicularis. In: Fire Effects Information System. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). 2008, July 6

Prickly rose plants are quite variable in morphological details including pubescence, glandularity, and fruit shape . Prickly rose is a deciduous shrub about 4 feet (1.2 m) in height with many fine roots in the top 8 inches (20 cm) of soil. Deep roots may extend to 55 inches (140 cm) . The main stems are usually covered with slender, straight bristles or prickles. The alternate leaves are pinnately compound with five to nine leaflets and conspicuous stipules. The pink or rose-colored flowers have numerous stamens and are borne singly on lateral branches. The globose, fleshy, red or orange-red hip has 10 to 30 achenes. Each achene is 0.15 to 0.2 inch (3.8-5 mm) long with stiff hairs along one side.

Information about subspecies (varieties) is summarized below:
Subspecies (variety) acicularis is octoploid (2n = 56). It has glandular pedicels and narrow sepals (less than 0.1 inch or 3 mm). Its leaves have five leaflets.
Subspecies sayi (variety bourgeauiana) is hexaploid (2n = 42). Its pedicels are glabrous and the sepals are wider than 0.1 inch (3 mm). There are five to nine leaflets in each leaf.

Article (website)  (2002)  
 
Taxon: Rosa acicularis Lindl. subsp. sayi (Schwein.) W.H. Lewis
Distributional range: Northern America
References: Lewis, W. H. 1959. A Monograph of the genus Rosa in North America. R. acicularis Brittonia 11:1-24
Synonyms:
Rosa acicularis var. bourgeauiana Crép.
Rosa acicularis var. engelmannii (S. Watson) Crép. ex Rehder
Rosa acicularis var. sayiana Erlanson

Article (magazine)  (2001)  Page(s) 393.  
 
R. acicularis var. engelmannii Crép. ex Rehd. Ploidy 6x
Pollen fertility 96.4%
Selfed fruit set 57.7%
Selfed Seed Set 25.1%

Book  (1996)  Page(s) 90, 114.  
 
p. 90: R. acicularis Needle-rose. The only species which is found in Europe, Asia and America, passing the Polar Circle. Deep pink, scattered large, single blooms. Short.

p. 114: R. acicularis saji Needle-rose.

Article (misc)  (1958)  Page(s) 242.  
 
In "Minor Forms of North American Species of Rosa," by Walter H. Lewis,
Rosa acicularis Lindl. subspecies Sayi (Schweinitz) f. plena
A form typical of Rosa acicularis Lindl. subspecies Sayi except that as many as fifteen petals occur in each flower. The form is known from only one locality, Moose Range, Saskatchewan.

Book  (1937)  Page(s) 78.  
 
Sayi Schwein (synonym of acicularis Lindl.) [ploidy] 42

Book  (1904)  Page(s) 1555.  Includes photo(s).
 
acicularis Lindl. var. Sayi Rehd. (R. acicularis var. Bourgeauiana Crép., partly)
Leaflets glandular and pubescent benearth, usually somewhat doubly glandular-serrate; flowers larger, often 2½ inches across; fruit usually globular. Ontario to British Columbia and Colorado.
var. Engelmanni Crép. in herbarium (R. Engelmanni Wats.) Similar to the preceding; leaflets distinctly doubly glandular-serrate; fruit oblong to 1 inch long. Colorado to British Columbia.